Stage 3 Sleep – Deep Sleep & Recovery
Stage 3 sleep, also called deep sleep or slow-wave sleep (SWS), is the most restorative stage of your sleep cycle. It typically makes up 15–25% of total sleep, especially in the first half of the night.
What Happens in Stage 3 Sleep?
- Brain waves slow to delta waves, the slowest and highest-amplitude brain activity.
- Muscles fully relax and blood pressure drops.
- Growth hormone is released, supporting tissue repair and immune system function.
- It is hardest to wake someone from Stage 3 sleep — if disturbed, people may feel groggy and disoriented.
Why Stage 3 Sleep Matters
Stage 3 is crucial for physical recovery and immune health. Without enough deep sleep, you may experience fatigue, lowered resistance to illness, and impaired physical recovery. It also contributes to memory consolidation and clearing waste from the brain.
Stage 3 Sleep and Your Nightly Cycles
Stage 3 dominates the first half of the night. As sleep cycles continue, deep sleep decreases while REM sleep grows longer. By morning, Stage 3 may be minimal or absent, replaced by lighter sleep and REM.
Tips for Supporting Deep Sleep
- Keep a cool, dark bedroom — deep sleep thrives in a low-stimulus environment.
- Avoid alcohol before bed, which can reduce slow-wave sleep quality.
- Exercise regularly, especially aerobic activity, which has been shown to increase deep sleep.
Learn More About the Sleep Stages
Deep sleep is just one of the essential stages your body needs each night. Explore the others here: